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Fishery Bulletin 111(3) 
2.0 
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1.6 
_ 1.4 
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>- 1.2 
1.0 - 
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76 0.8 - 
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H 0.6 j 
0.4 
0.2 j 
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Z from tag-recovery modeling 
95% Cl for tag estimate 
o Z estimates from 2008 GARM 
2003 
2004 
2005 
2006 
Year 
Figure 3 
Estimates of total mortality ( Z ), with 95% confidence intervals 
(CIs), of Yellowtail Flounder (Limanda ferruginea) from 2003 to 
2006 from tag-recovery modeling in this study and the stock as- 
sessments from the 2008 Groundfish Assessment Review Meeting 
(GARM) of the Northeast Fisheries Science Center. 
mortality), survival from the tagging process, tag re- 
tention, and tag reporting (Brownie et al., 1985). 
The mortality estimates derived from the tagging 
data corroborate stock assessment estimates; however, 
tag estimates could be inflated if a model assumption 
was violated. For the tagging models, all marked fish 
were assumed to have the same probability of sur- 
vival and recapture by the fishery. This assumption is 
often violated when newly released fish do not fully 
mix with the population and have a different recap- 
ture probability (Hoenig et ah, 1998). A close examina- 
tion of the full residual matrix for Yellowtail Flounder 
did not reveal any patterns consistent with nonmixing, 
which is typically represented with a consistent resid- 
ual along the recovery diagonal (Latour et al., 2001). 
Tagging-induced effects, both directly induced mortal- 
ity and short-term tag loss, also could affect survival 
estimates. Experiments with tanks and cages designed 
to test the tag retention and tag-induced mortality of 
Yellowtail Flounder have indicated that these effects 
were not a concern (Alade, 2008). Any possible influ- 
ence from these 2 effects likely would remain constant 
throughout the study and would not influence the sur- 
vival estimates significantly. 
Finally, the tag-recovery models used in this study 
did not estimate tag loss and tags were assumed not 
lost or missed. A fish that loses its tag is equivalent to 
a dead fish when it comes to the estimation of survival 
(Brownie et al., 1985). The Peterson disc tags used in 
this study are secure tags that pass through the body 
of a flounder and are anchored on both the 
dorsal and ventral surfaces. These tags have 
been widely applied in fish tagging studies 
and are known for a very high retention 
rate (Thorsteinsson, 2002). In addition, a 
long-term holding study with some fish held 
for more than 1 year showed 100% tag re- 
tention, and therefore tag loss was expected 
to be minimal (Alade, 2008). 
Although the tag-recovery estimate of 
survival is consistent with results from age- 
based stock assessments, several aspects of 
this tagging study should be considered in 
future assessments. The difference in recov- 
ery rate between the sexes indicates that 
population dynamics may differ between 
males and females. The lower recovery rate 
of males could be a result of greater natural 
mortality — a finding that is consistent with 
sexually dimorphic growth rates and maxi- 
mum sizes of Yellowtail Flounder (Lux and 
Nichy, 1969). However, sex-based recovery 
rates also could result from differences in 
catchability between sexes. 
The possibility of substantial movement 
between stock areas (e.g., from southern 
New England to Georges Bank) may also 
influence population dynamics of Yellowtail 
Flounder (Hart and Cadrin, 2004). Analyses 
of simulated release and recapture data, with a data 
structure consistent to the data used in this study, 
indicate that movement and mortality cannot be si- 
multaneously estimated because of highly correlated 
movement parameters (Alade, 2008). Therefore, simul- 
taneous estimation of both movement and mortality 
may require an integrated analysis of data from tag- 
ging surveys, fisheries surveys, and resource surveys 
(Maunder, 2001; Goethel et al., 2010). 
A summary of all published yellowtail flounder 
movements off the northeast United States, including 
those reported here, has revealed that juveniles and 
adults do not frequently move among fishing grounds 
(Cadrin, 2010). The movement from the southern New 
England-Mid-Atlantic stock area to the Georges Bank 
stock area observed in the study described in this ar- 
ticle is greater than the movement reported in previous 
studies. However, most releases in the southern New 
England-Mid-Atlantic stock area were near the bound- 
ary because that location was the only one sampled in 
the stock area that had high densities of Yellowtail 
Flounder. The pattern of tag recoveries (Fig. 5) and 
previous analyses of movement trends from surveys 
(Cadrin, 2010) indicate that the southwestern portion of 
Georges Bank and Nantucket Shoals is an area of stock 
mixing, and that relative stock size may influence stock 
composition in that area. Although the study described 
here was not designed to estimate seasonal movement, 
the results of this research are consistent with those of 
previous tagging studies of Yellowtail Flounder off New 
